The present invention relates to the use of linear accelerometers for inertial measurement and, in particular, to an inertial measurement unit in which an arrangement of fixed linear accelerometers measures angular acceleration, angular velocity, linear acceleration and linear velocity.
Due to practical operational limitations of gyroscopes, various inertial measurement units incorporating linear accelerometers have been developed to measure angular acceleration and angular velocity in addition to linear acceleration and linear velocity. Such units require that some or all of the linear accelerometers be driven cyclically to provide output which may then be processed to determine angular acceleration and velocity. In some units, the linear accelerometers are spun or rotated around an axis, while in others they are vibrated or dithered about or along an axis. Regardless, while overcoming the limitations of gyroscopic devices, the necessary cyclical drive mechanism adds a further level of complexity and cost to these units. In addition, complex mathematical derivations necessary to process signals produced by driven liner accelerometers have required simplifying assumptions which are the source of unacceptable measurement errors in some applications.
Accordingly, the need exists for improved inertial measurement units which avoid the complexity, cost and problems experienced with devices having cyclically driven linear accelerometers.